1. Field of the Invention
This invention relates to a camera and, more particularly, to monitor display for confirmation of composition at photographing with a digital camera or control of what is called through-image display.
2. Description of the Related Art
When a composition of a subject is confirmed on a digital camera, through-image display can be employed besides an optical viewfinder using a lens. The through-image display is a technique of displaying a subject image made incident on a digital image pickup unit, on a monitor such as a liquid crystal display (LCD) or the like at a real time as it is. Movement of the subject can be observed at a real time on the monitor, similarly to the optical viewfinder. The through-image display is also called movie mode. At the through-image display, however, the image pickup unit and the monitor are in an operated state, and many currents are thereby consumed for a long time. For this reason, the battery life becomes shorter as more time is spent for framing at determination of the composition.
On the other hand, a camera user can execute photographing while watching through an optical viewfinder of the digital camera, similarly to a conventional film camera. At the through-image display, however, photographing can be executed in more natural attitude than an attitude of bringing a face close to an eyepiece of the camera. In addition, the user can raise the camera over the head or lower the camera position to execute photographing without watching through the optical viewfinder. For this reason, a general user tends to prefer photographing employing the through-image display to photographing using the optical viewfinder. Therefore, as a measure of preventing the battery life from being short, it is required not only to recommend the user to merely use the optical viewfinder, but also to restrict the power consumption in the through-picture mode.
In other words, power is required to drive a display system, an image pickup system, an image processing system and the like of the digital camera, unlike the film camera. A considerable amount of currents are spent in the digital camera. Thus, short battery life is a serious problem for the digital camera. For example, if the battery is dead at a place where a battery for replacement does not sell, photographing cannot be continued. In this case, good memories cannot be saved.
Moreover, if composition is to be determined by using not the optical viewfinder, but the monitor such as the LCD, power is spent by electronic circuits of an image pickup system, an image processing system and a display system until the user determines the composition. Thus, the battery life is further wasted.
To solve this problem, Jpn. Pat. Appln. KOKAI Publication No. 2001-86382 discloses a technique of reducing power consumption by reducing the number of pixels of the image pickup means used at the through-image display.